1. Field of the Invention
This invention relates to endless belt conveyors the belt of which is stretched between two pulleys or drums one of which is a drive pulley provided with belt guiding means at least at one of the belt ends.
2. Description of the Prior Art
The invention relates more particularly to conveyors of the type disclosed in U.S. Pat. No. 3,518,940 and equipped with a very thin belt having a thickness in the range of 1/10th of a millimeter. Such conveyors are used, in particular, in high intensity magnetic separators intended for separating materials of weak magnetic susceptibility and including a roll consisting of a set of disc-shaped pole pieces and permanent magnets mounted alternately on a shaft, which roll constitutes the conveyor drive pulley. In these machines, the belt is used, on the one hand, to convey the material to be separated on the roll and to remove the magnetic particles, and, on the other hand, to protect the roll against clogging up and abrasion. The belt must be made of a non-magnetic material and it must be as thin as possible in order not to affect significantly the roll performance.
In order to prevent the belt from driving transversely, it is necessary to guide it at one of its ends or at both of them. Accordingly, it has been proposed to provide at least one of the drive pulley ends with a circular row of studs fitting into holes punched along the edge of the belt. This cannot be done without precautions in conveyors equipped with a very thin belt for the following reasons: because of manufacturing tolerances and of the belt stretch under tension, there are necessarily differences between the distance between the studs and the distance between the belt holes so that, after a certain time of operation, the studs and the holes are no longer coincident with each other, and the former exert on the edges of the holes forces which tend to slide the belt on the pulley and which would result in tearing a very thin belt.